1. Field of the Disclosure
The present disclosure relates to segmentation of electronic images to specific regions of interest in a field of view, such as for example tissue structures in medical imaging; and also for improvements to clinical magnetic resonance spectroscopy (MRS), for example, to single or multi-voxel MRS; and also to the automated prescription of voxels within regions of interest where MRS is to be performed, such as for example in intervertebral discs.
2. Description of the Related Art
Conventional systems and methods for prescribing voxel size and position within a region of interest (ROI) for magnetic resonance spectroscopy (MRS) applications involve manual techniques by an operator technician working from magnetic resonance imaging (MRI) images taken prior to the prescription operation. This standard approach suffers from various drawbacks. These include, for example but without limitation: (1) limitations in the ability to accurately define the ROI boundaries within which the voxel should be fit; and (2) drawbacks from manual prescription such as (a) time required to perform the prescription under time constraints of an overall exam, and (b) achieving optimal trade off between (i) maximizing voxel volume within the ROI for maximum signal:noise ratio (SNR) and (ii) confining the voxel within only the ROI boundaries and avoiding overlap with adjacent tissues outside of the ROI—which can potentially blend chemical information between tissue constituents within the ROI and extraneous constituents outside of the ROI into the acquired spectra, and thus potentially compromise diagnostic interpretation and results.
In addition, diagnostic imaging exams are typically reliant upon a fixed positioning of the patient during the exam, and may be compromised by patient motion during the image acquisition. This also directly applies, for example but without limitation, to MRS exams. In particular, an accurate voxel prescription which aligns the region for MRS data acquisition to an ROI will become mis-registered with that tissue ROI if the patient moves after the prescription but before completion of the image acquisition. The information acquired may blur pre- and post-motion information during the image acquisition process, and/or may introduce chemical information from tissues which originally were extraneous to the voxel location, but due to the motion were introduced into the voxel location due to moving the anatomy relative to the fixed voxel.
These issues represent particularly poignant challenges for conducting MRS in musculoskeletal applications, in particular skeletal joints, and still more particularly intervertebral discs. This is also especially for example the case in settings where, but without limitation, target tissue ROIs have limited volumes, requiring maximum voxel volume to achieve sufficient SNR, and are located adjacent to other tissues (e.g. next to or between bones, such as for example in skeletal joints) with dramatically different chemical constituents than the ROI—and thus could introduce significant unintended chemical signatures into acquired spectra if there is voxel overlap outside the ROI or due to patient motion during an exam.
In the particularly unique setting of intervertebral discs, the disc tissues are bordered by opposite end-plates of superior and inferior vertebral bodies, in addition to laterally by a number of different tissue structures (e.g. spinal canal). These introduce dramatically higher contents of lipid (in the case of bony structures), and water (e.g. in the case of spinal canal), than in the disc itself. Moreover, the discs are relatively small for conventional MRS voxel purposes. This is further confounded by prevalent disease conditions where diagnostic imaging (and MRS in particular) may often be indicated, such as degenerative disc disease, that are specifically characterized by abnormally reduced disc height and volume as well as dehydration and dessication of the disc tissue. These issues represent a landscape that is more challenging for defining (e.g. “segmenting”) the disc material ROI from surrounding structures, such as for example for diagnostic image analysis or to define regions for directed therapies. In particular context of MRS, they also represent an environment for inherently low SNR, and accordingly require maximum possible voxel volume to be prescribed. Furthermore, the relatively small geographies and close proximities of discs relative to their bordering tissues heightens the risks and potential impact of patient motion during a disc-related imaging exam, such as especially but not limited to disc MRS exams.
These issues noted above are uniquely implicated in the ability to successfully perform single voxel spectroscopy in skeletal joints, and especially intervertebral discs, though they also relate to multi-voxel spectroscopy, and other imaging considerations (MR-related or otherwise), and other tissue structures.